Effects of Nitrogen Deposition on Typical Hydrolytic Enzyme Activities by Fluorimetric Assay

Soil properties and five hydrolytic enzyme activities under different simulated nitrogen deposition treatments were determined under semi-arid grassland in Northern China. Significant acidification was observed under N addition treatments. Highest values of soil total carbon, phosphorus and olsen-P concentration was observed in medium level of N application. Soil acid phosphomonoesterase, phosphodiesterase and N-acetyl-beta-D-glucosaminidase activities increased with N amendment. The beta-D-glucosidase and arylsulfatase activities were stimulated under medium level of N addition. The principal components analysis showed that N deposition might influence soil enzyme activities indirectly through soil pH, total carbon, total phosphorus and olsen-P concentration. Furthermore, the principal component analysis also showed similarity of N-2.8 and N-4.0 treatments, which indicated N saturation at 2.8 mol N m(-2) yr(-1) in the study area.